After releasing SQL Server 2005 SP4 on Friday (you can read more about it here), the release services team did not hang up their hats for the Christmas holiday, but continued working on other releases.

KB #2438344 : Cumulative update package 13 for SQL Server 2005 Service Pack 3
This brings your SQL Server 2005 SP3 build number to 9.00.4315

KB #2438347 : Cumulative Update package 5 for SQL Server 2008 R2
This brings your SQL Server 2008 R2 build number to 10.5.1753

NOTES:

1. You will not be able to apply Cumulative Update #13 to SQL Server 2005 Service Pack 4!  This release is for SQL Server 2005 Service Pack 3 only.  I still suspect that we won't see a cumulative update for SP4 until a month into the new year – however maybe it will contain the fixes from both CU#12 and CU#13.
    
2. You cannot apply Cumulative Update #5 to SQL Server 2008!  This release is for SQL Server 2008 R2 RTM only.